Networks transfer electronic information between different locations. Broadband networks differ from other networks in that they transfer a relatively large amount of information during each unit of time. Future broadband networks are expected to convey video signals for business, educational and residential applications. Such networks may provide services such as broadcast-like video distribution, individual access to video program libraries, video telephone, video conferencing, and the like. Any one of such services may, for example, communicate signals having data transfer rates of up to 50 Mb/s or more.
In order to effectively serve a large number of customers, a broadband network includes switching nodes. At switching nodes, broadband signals are routed along selected paths so that desired signals are delivered from signal sources to targets.
Numerous problems are faced by a broadband, real-time switch that accommodates a large number of connections. These problems result, at least in part, from the high data transfer rates associated with broadband communications. In short, a tremendous amount of data need to be processed or otherwise transferred through the switch during every unit of time, and the larger the number of connections supported by the switch, the greater the amount of data which need to be processed.
A practical broadband switch should be able to efficiently support a variety of communication services, whether or not such services require unidirectional or bidirectional signal traffic. For example, although unidirectional broadcast-like services are currently available, bidirectional services such as video conferencing and other interactive services that utilize point-to-point connections may be in high demand in the near future. Unfortunately, switching systems designed to efficiently handle broadcast-like communications may not be capable of efficiently supporting bidirectional signal traffic, and vice versa. Such systems may not be able to adapt to long term trends in upstream and downstream signal traffic demand. In addition, conventional network switches may not be able to adapt to large or rapid variations in the amount of upstream versus downstream traffic.
An adaptable network switch may require less switching hardware than a rigidly designed switch having equivalent switching capabilities. A reduction in the number of physical components is desirable to conserve space and to lower engineering, manufacturing, and maintenance costs. For example, given a specific mix of upstream and downstream switching capacities, a switching circuit that adapts to upstream and downstream traffic volume requires fewer components than an equivalent switching circuit that employs a fixed number of upstream circuits and a fixed number of downstream circuits. If the actual volume of upstream and downstream traffic is not proportional to the respective number of fixed upstream and downstream circuits, then the circuits are not optimally allocated and switching capacity is wasted.
Switching capacity is also wasted when communication signals are delivered to a network switch without being requested from a downstream customer. Switching circuits become busy with signal traffic and the probability of blocking increases when signals are unnecessarily brought down to the network switch. The frequency of signal blocking can also increase if traffic volume is not evenly distributed among unoccupied or sparsely-occupied switching circuits. In addition, switching speed may be sacrificed if the network switch distributes signal traffic in a random or unstructured manner.